The peanut plant has high plasticity and great adaptability to adverse conditions, including drought. To mitigate the negative effects of drought on legumes, nitrogen-fixing microorganisms have been investigated in some plant species, such as soybeans and beans. We analyzed the role Bradyrhizobium strains in peanut genotypes subjected to water deficit by means of plant growth, physiological and gene expression analysis. The research was conducted under greenhouse conditions with the runner peanut genotypes (IAC Runner 886, 2012-33 and 2012-47) and two Bradyrhizobium strains (ESA 123 and SEMIA 6144). After 20 days of germination, the water supply was completely interrupted and gas exchange analysis were carried out using an infrared gas analyzer, up to the 10 th day of stress. Leaves were collected for the analysis of proline content and the expression of NCED and ERF8 genes. Analyses of plant height (PH), shoot dry mass (SDM), root dry mass (RDM), number of nodules (NN) and nodule weight (NW) also were ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 18 (4): gmr18379 S.L. Brito et al. 2 performed. The peanut shoots inoculated with the Bradyrhizobium strains obtained the best results. The genotypes inoculated with the ESA 123 strain obtained superior responses compared to the nonstressed treatment inoculated with the same bacteria and the stressed control without bacterial inoculation. In the ESA 123 inoculated treatments, the water stressed plants had higher RDM (28.5% higher, on average), NN (two fold higher), and gene expression (approximately six and threefold higher for ERF8 and NCED genes, respectively). The increase in the expression of NCED and ERF8 genes, in the three genotypes inoculated with ESA 123, suggests a key role of this inoculant in the activation of metabolic cascades for plant protection under water deficit.

Seed treatment with fungicides is an important practice for the control of phytopathogens in peanut crops. However, these products can harm rhizobacteria (Bradyrhizobium) and inhibit processes such as biological nitrogen fixation. This study aimed to verify the effects of the treatment of peanut seeds cv. BR1 inoculated with Bradyrhizobium spp. with fungicides. The experiment was conducted in a greenhouse, using two combinations of fungicides [C1: carboxin (200 g L-1) + tiram (200 g L-1); C2: pyraclostrobin (25 g L-1) + thiophanate methyl (225 g L-1) + fipronil (250 g L-1)] and one control without fungicide; two inoculants based on Bradyrhizobium spp. (SEMIA 6144 and ESA 123) and one control with a nitrogen chemical source (ammonium nitrate). The experimental design was completely randomized, in a 3 (2 with fungicide and 1 without fungicide) x 4 (2 inoculations based on rhizobia, 1 N mineral source and 1 without N) x 2 (1 or 2 inoculants applications) factorial scheme, with 5 replications. The root and shoot dry mass, plant height, nodulation and leaf nitrogen accumulation were evaluated. The application of both combinations reduced the number of nodules on plant roots, mainly for C1. The vegetative growth and nitrogen in the leaves were affected by C1, whereas, for C2, there were increments higher than for the control without fungicides. ESA 123 was more tolerant to the effects of fungicides on nodulation. Regarding the number of inoculations, there was an increase in the nitrogen rate with two inoculations. C2, despite affecting the nodulation, was less toxic to the inoculants SEMIA 6144 and ESA 123.